1. Field of the Invention
This invention relates to a vehicle AC generator, and particularly relates to an output terminal structure of a vehicle AC generator.
2. Description of the Related Art
FIG. 6 is an oblique perspective view showing a conventional rectifier applied to a vehicle AC generator, and FIG. 7 is a cross sectional view of the main part describing the state of attachment of a conventional rectifier.
In FIG. 6 and FIG. 7, a rectifier 120 comprises: a plurality of positive electrode side and negative electrode side diodes 20, 21 for full-wave-rectifying the three-phase AC; first and second cooling plates 122, 123 for cooling positive electrode side and negative electrode side diodes 20, 21, respectively; insulators 24, 27 for insulating the first and second cooling plates 122, 123; a circuit board 125; and an output terminal bolt 126. Here, the positive electrode side and negative electrode side diodes 20, 21 make up the first and second diodes, respectively.
The first cooling plate 122 is formed approximately like a horseshoe, and the positive electrode side diodes 20 are attached on the main surface 122a thereof side by side in the circumferential direction. Then, a heat radiating fin 122b is provided rising from the rear surface (surface on the opposite side of the main surface) of the first cooling plate 122. Furthermore, three flange parts 130, 131, 132 are provided at both end parts in the circumferential direction and at the middle part in the circumferential direction of the first cooling plate 122, respectively. Each of the flange parts 130, 131, 132 is provided so that it may rise up from the main surface 122a of the first cooling plate 122 and after that, it may extend outward in the radial direction. Then, an output terminal bolt inserting through hole 134 is pierced in the extending-out end in the radial direction of the flange part 130 provided at one end part in the circumferential direction of the first cooling plate 122, and attaching screw inserting through holes 133 are pierced in the extending-out ends in the radial direction of the residual flange parts 131, 132.
The second cooling plate 123 is formed approximately like a horseshoe with a diameter larger than that of the first cooling plate 122, and the negative electrode side diode 21 is attached on the main surface 123a thereof side by side in the circumferential direction. Then, one output terminal bolt inserting through hole 138 and two attaching screw inserting through holes 135 are provided at both end parts in the circumferential direction and at the middle part in the circumferential direction of the second cooling plate 123, so as to correspond to the output terminal bolt inserting through hole 134 and the attaching screw inserting through holes 133 provided in the first cooling plate 122, respectively.
The circuit board 125 is a resin molded part having wiring insert-molded for constituting the diode bridge of the positive electrode side and negative electrode side diodes 20, 21, and it is formed approximately like a horseshoe similar to that of the second cooling plate 123. Then, one output terminal bolt inserting through hole 137 and two attaching screw inserting through holes 136 are provided at both end parts in the circumferential direction and at the middle part in the circumferential direction of the circuit board 125, so as to correspond to the output terminal bolt inserting through hole 134 and the attaching screw inserting through holes 133 provided in the first cooling plate 122, respectively.
The insulator 24 is made of, for example, phenol resin, and is formed like a cylinder having a flange part 24a at the peripheral central part. The insulator 27 is made of, for example, phenol resin, and is formed like a cylinder having a flange part 27a at one end part. Furthermore, in the output terminal bolt 26, a knurled groove 26a is provided on the anti-take-out side, and a male screw part 26b is provided on the take-out side.
For assembling this rectifier 120, first of all, the insulator 24 is inserted into each attaching screw inserting through hole 135 of the second cooling plate 123 so that the flange part 24a may come into contact with the main surface 123a. Similarly, the insulator 27 is inserted into the output terminal bolt inserting through hole 138 of the second cooling plate 123 so that the flange part 27a may come into contact with the main surface 123a. Next, the first cooling plate 122 is arranged so that the insulator 24 may be inserted into each attaching screw inserting through hole 133. Consequently, the first and second cooling plates 122, 123 are coaxially arranged so that the main surfaces 122a, 123a may be positioned at the same surface, and are arranged so that the positive electrode side diode 20 and the negative electrode side diode 21 may face to each other. Furthermore, the circuit board 125 is overlapped onto the main surface 123a of the second cooling plate 123 so that the insulator 24 is inserted into each attaching screw inserting through hole 136. Consequently, the connecting terminal 125a of the circuit board 125 is held between the terminals 20a, 21a of the positive electrode side and negative electrode side diodes 20, 21 that are facing to each other, and joined by soldering. Next, the output terminal bolt 26 is inserted into the output terminal bolt inserting through holes 134, 138 of the first and second cooling plates 122, 123 from the output terminal bolt inserting through hole 137 of the circuit board 125. Then, the knurled groove 26a of the output terminal bolt 26 is pressed into the output terminal bolt inserting through hole 134 of the first cooling plate 122, and the output terminal bolt 26 and the first cooling plate 122 are electrically connected, and the rectifier 120 shown in FIG. 6 is assembled.
As shown in FIG. 7, the first and second cooling plates 122, 123 and the circuit board 125 are fastened together by screwing the attaching screw 40 inserted into each of the attaching screw inserting through holes 133, 135, 136 into the screw hole 2a provided in the rear bracket 2, and thereby the rectifier 129 assembled like this is attached. The take-out side of the output terminal bolt 26 connected to the first cooling plate 122 is extending out of the opening 2b pierced in the rear bracket 2. Then, by fastening the output terminal fastening nut 50 screwed onto the male screw part 26b of the output terminal bolt 26, the insulating bush 41 made of phenol resin and mounted on the opening 2b of the bracket 2, the first and second cooling plates 122, 123, and the circuit board 125 are fastened together and fixed to the rear bracket 2.
Then, for connecting the vehicle side connecting terminal 42 made of copper material to the output terminal bolt 26, the connecting terminal 42 is fitted onto the take-out side of the output terminal bolt 26, and furthermore, the nut 44 is screwed onto the male screw part 26b. Then, by fastening the nut 44, the connecting terminal 42 is fastened and fixed onto the outer end surface of the nut 50. Here, the outer end surface of the output terminal-fastening nut 50 constitute the fastening seat.
Here, the first and second cooling plates 122, 123, the circuit board 125, and the insulating bush 41 are fastened together and fixed to the rear bracket 2 by the fastening force of the output terminal fastening nut 50, and therefore, even if the vibration based on the weight of the wire harness or the like from the vehicle is transmitted to the vehicle side connecting terminal 42, there is no displacement in the axial direction of the output terminal bolt 26, and initially, damage or the like of the rectifier 120 can be prevented. Furthermore, since the fastening force of the nut 44 is received by the outside surface of the output terminal-fastening nut 50 constituting the fastening seat, the fastening force of the vehicle side connecting terminal 42 is ensured initially.
In a conventional AC generator, the distance between the fastening nut 44 and the output terminal fastening nut 50 is short, and the wire harness is held by the tensile stress based on the elongation of the output terminal bolt 26 at that part, and therefore, as understood from Hook""s law: "sgr"=Exc2x7xcex=Exc2x7(xcex94A/A), in a conventional device, the elongation xcex94A at that part is small under a condition that the fastening torque is fixed ("sgr" is fixed) since A is short. Therefore, the displacement in the circumferential direction of the nut 44 corresponding to the control upper limit value to the lower limit value of the torque is small, and there has been such a problem that the control for performing the fastening by a specified torque is difficult when fastening the nut 44. Furthermore, when considering the case where the fastening is performed by a torque out of a range from the upper limit of the control value to the lower limit of the control value, in the state where the fastening force exceeds the control upper limit value and the fastening is too tight, the tensile stress is extremely increased and the output terminal bolt 26 is broken. Conversely, in the case of the state where the fastening force is below the control lower limit value and the fastening is loosened, there has been such a problem that the torsional moment acts on the nut 44 to cause a malfunction of slipping-off of the nut 44 only by a weak vibration from the wire harness side.
Even in the case where the nut 44 is fastened by a control value, when an excessive torsional moment acts by a vibration from the wire harness, the fastening torque is extremely lost only by the occurrence of loosening because of a little displacement, and the slipping-off of the nut 44 is caused. Conversely, in the case where the nut 44 is fastened by a minute displacement, there has been such a malfunction that the tensile stress is extremely increased in the bolt 26 to break the bolt 26. Furthermore, there has been such a problem that xcex94A is small and therefore, in the case where a compressive or tensile force acts on the output terminal bolt 26 in the axial direction of the output terminal bolt 26 by the vibration from the wire harness, the loosening of the nut 44 is caused by the decrease of the fastening force of the wire harness and the slipping-off of the nut 44 is caused when the number of cycles of the vibration is increased.
The present invention is made for solving such a problem, and it is an object to obtain a vehicle AC generator, in which it is easy to control the suitable fastening torque and in the meantime, the slipping-off of the nut is prevented and the damage of the output terminal bolt at the wire harness holding part caused by the excessive fastening of the bolt is prevent, so that the connection reliability of the vehicle side connecting terminal may be improved.
A vehicle AC generator according to a first aspect of the invention comprises:
a bracket having an opening;
a cylindrical insulating bush mounted on the opening;
an output terminal bolt inserted through the insulating bush to project out of the bracket and fixed to the bracket;
a fastening nut capable of being screwed onto the output terminal bolt to mount a vehicle side connecting terminal; and
a bush provided between the insulating bush and the vehicle side connecting terminal by being fitted onto the output terminal bolt,
wherein the fastening nut is screwed onto a screw part on a take-out end part side of the output terminal bolt so that the vehicle side connecting terminal is held between the bush and the fastening nut.
In a second aspect of the invention, there is provided a vehicle AC generator according to the first aspect of the invention, wherein the bush having:
a bushing part loosely fitted onto the output terminal bolt; and
a fixed part fixed to the output terminal bolt on the opposite side of the vehicle side connecting terminal of the bushing part.
A vehicle AC generator according to a third aspect of the invention comprises:
a bracket having a first opening;
a cylindrical projecting part formed on the bracket projecting to surround the first opening, the cylindrical projecting part having a second opening at the projecting end;
a cylindrical first insulating bush mounted on the first opening;
a cylindrical second insulating bush mounted on the second opening;
an output terminal bolt inserting through the first and second insulating bushes to project out of the bracket, the output terminal bolt fixed to the bracket;
a fastening nut capable of being screwed onto the output terminal bolt to mount a vehicle side connecting terminal; and
a bush provided between the first insulating bush and the vehicle side connecting terminal by being fitted onto the output terminal bolt, the bush having a bushing part loosely fitted onto the output terminal bolt and a fixed part fixed to the output terminal bolt between the first insulating bush and the second insulating bush,
wherein the fastening nut is screwed onto a screw part on a take-out end part side of the output terminal bolt so that the vehicle side connecting terminal is held between the bushing and the fastening nut.
In a fourth aspect of the invention, there is provided the vehicle AC generator according to any one of first to third aspects of the inveniton, further comprising:
a rotor rotatably supported by the bracket;
a stator fixed to the bracket to surround the rotor on the peripheral side of the rotor;
a rectifier including:
a first cooling plate having a plurality of first diodes, the first cooling plate fixed to the bracket; and
a second cooling plate having a plurality of second diodes whose polarity are different from that of the first diodes, the second cooling plate fixed to the bracket
wherein the bracket is made of metal.
In a fifth aspect of the invention, there is provided the vehicle AC generator according to any one of the first to fourth aspects of the invention, wherein a length of the bushing part is set to two times or more as large as an outside diameter of the output terminal bolt.
In a sixth aspect of the invention, there is provided the vehicle AC generator according to any one of the second to fifth aspects of the invention, wherein the fixed part includes a nut having a female screw.